The purpose of analog multiplexing circuits is to select one input from a number of analog inputs and reproduce the selected input faithfully at an output. Ideally, the multiplexer is wideband, has no feed through of unselected inputs, and can handle a reasonably wide range of input voltages from the unselected channels without causing damage to the internal circuitry of the multiplexer.
Unfortunately, high-speed semiconductor processes do not support large voltages without breakdown. Unless a schottky diode is available, the only high-speed junction available for switching function is a transistor's base-emitter (or equivalent) junction, which can be limited to as little as 1.5V of reverse bias, severely limiting the magnitude of input signals. Unfortunately, schottky diodes can not be produced using many types of semiconductor processes. Accordingly, it would be beneficial to provide an analog multiplexing circuit that can handle large input voltages and achieve high (e.g., GHz) frequency responses, without requiring a schottky diode.